We are coming out with an "Internationalized" version of the product as of release 6.3 (forthcoming) supporting Japanese. Between now and then you will just have problems with (e.g.) file names or registry names/values that are not English. If you have English data it should be OK. One of the areas that will most likely fail is Windows Services as I believe it will always return, among other data, Japanese descriptions which will of course not work well.
You might want to talk to your sales rep to get details.